1. Field of the Invention
The present invention relates to a sound data processing system, and more particularly to a sound data interpolating circuit which, when an occurrence of a sample error in a sound Pulse-Code Modulation (PCM) data cannot be corrected by an error correction circuit, can, in an individual double error, perform an average value interpolation against prior and subsequent samples for every sound channel, and can, in a continuous double error, perform a preinterpolation, to thereafter improve tone quality.
2. Description of the Prior Art
In order to reproduce sound PCM data in an original aural signal, a decoding is performed, and then error correction and compensation are performed to thereby detect whether or not there is an error.
Conventionally a Bose-Chaudhuri-Hocquenghem (BCH) error correction circuit performing error correction per 64-bit sample has been utilized. The 64-bits are comprised of an information bit block of 56-bits, an error correction bit block of 7-bits and redundancy bit of 1-bit, and when an error occurs in the information bit block, the error is corrected by an error correction bit.
However, though the BCH error correction circuit can correct an error of one bit per sample generated in a transmission process, a correction of a double error covering more than 2 bits per sample cannot be performed by the BCH error correction circuit, which instead outputs a double error signal. Data wherein the error correction cannot be performed by the BCH error correction circuit is evidenced as noise.
For example, in U.S. Pat. No. 4,451,921, entitled "PCM Signal Processing Circuit" clock noise is produced by discontinuities of PCM signal data in a wrinkled area of the like of a magnetic tape, and interpolation to data situated prior to and after the PCM signal data is performed to thereby prevent the generation of clock noise within an audio signal. Though this system can prevent noise regeneration in the cases of special variable speed regeneration or editing or the like within the audio signal, the correction of double errors has not been performed.
As seen from the foregoing, the signals which have not undergone error correction are outputted as noise to thereby degrade audio reproduction.